I'd be curious what the equivalent idea of what you are doing (by posting here as AMA) would be if you weren't Eric Ries posting on HN. So for Eric Ries this is "lean" (or what used to be known as "gorilla marketing") but for someone who doesn't have name recognition what is the equivalent? [1]
[1] Simply recognizing that someone without name recognition doing something similar on HN is not assured of getting any attention.
Let's be honest: I almost didn't make the front page. My post got to about #25 on /newest with only like 9 upvotes. If it had rolled over to page two, I doubt I would still be answering questions right now. So no, I don't think this kind of technique is useful for marketing if you don't have name recognition.
However, there are many other ways to build rep in a community like HN without being famous. I bet if any of the highest-karma posters did an AMA they would get a lot of attention. Personally, I'd be fascinated to learn more about who they are.
My personal feeling is that the high karma that you are speaking of is not a good use of time (for that reason). I know it has helped tptacek and some others but it takes considerable time (and is a distraction) to comment on HN and essentially if you do it, you do it for fun and to learn. And if something comes from it then that's icing on the cake.
I actually picked up a considerable amount of side consulting by being a regular commenter on a well known blog. While I make money from that side consulting (near 6 figures), it's actually a drain on how I make money in other ways. It almost doesn't pay (but it's fun). [1] However the time it took me to earn enough of a reputation which led (in an indirect way) to the consulting (and contacts) was really a poor use of my time.
A better idea time wise, to jump start reputation, and build a rep (in a community like HN if that is what you are trying to do) would be to attempt to do things that are remarkable and get attention. Then people might talk about you and you will have the reputation that you seek that will bring other things that you need.
[1] I also get to meet many interesting people and contacts as well.
Being an active participant on HN has been very helpful to me professionally. HN karma, on the other hand, has not. The only thing that ever came from karma for me was a TechCrunch interview about HN.
There are great commenters who are very well-known who don't rank anywhere on the leaderboard. 'pbsd is a well-known cryptographer. 'tzs is the best commenter on HN. 'carbocation is a doctor/medical researcher.
Being engaged and available is important. The leaderboard is a really warped assessment of that. HN should get rid of it, along with the whole karma system.
An easy start: continue scoring comments, but stop revealing per-user karma totals.
I don't think anyone needs an AMA from me or Patrick McKenzie. The Ries AMA is interesting because he isn't a regular, and has interesting things to say.
True that, HN wasn't designed to be a forum, and there is virtually no point in having a karma system since this is as far as I know not a for profit site, and the quality of this site itself draws people so there is little point for providing karmas to keep people interested
Matasano Security, the company you founded, was acquired by NCC Group for $13 million in cash. You probably saw a good chunk of that money, and one would assume you'd be well off enough to not work for $39.54/wk. Why do it anyway?
[1] Simply recognizing that someone without name recognition doing something similar on HN is not assured of getting any attention.